These things are rare, but if you were in the right spot for 25 minutes at SXSW 2010, you no longer felt like you were in the middle of a chaotic industry clusterfuck. This was in Buffalo Billiards, a cheesed-out pool hall on 6th street, chaotic-clusterfuck ground zero, but there’s a decent chance that the three women onstage didn’t know what a chaotic clusterfuck even was, that they’d banished even the idea of it from their souls. Those three women were Mountain Man, a folk group from Bennington, Vermont, and they pushed the whole Fleet Foxes thing as far as it could possibly go by eliminating any extraneous instrumentation and basically just doing campfire singalongs onstage in front of us. They mostly sang a cappella, with one of them occasionally plucking at a guitar, and they said, during the show, that it was the first time they’d ever sung into microphones. (The mere fact that a band could land an SXSW without previously using microphones was, and is, just mind-bogglng.) They didn’t face the audience when they sang; they faced each other. They started the show with a group hug. I think they may have been barefoot. The whole thing was so utterly endearing, so devoid of pretense. And the way they sang, in warm and intimate and guileless folk harmony, was just entrancing. Now, four years later, one of those three women is singing over electronic clicks and whirrs and thumps, sometimes through Auto-Tune — a surprising turnaround, to say the least. But she’s kept that same intimate, wide-eyed energy, that weird basic purity. Listening to Amelia Meath on her side project Sylvan Esso’s self-titled debut, it’s easy to imagine her still on that stage, singing to her friends, not quite sure how to hold a microphone right. She’s let the world in, but she hasn’t let it fundamentally change what she’s doing.

The other half of Sylvan Esso is Nick Sanborn, who just joined Megafaun as a bassist last year. You’d expect a Mountain Man/Megafaun side project to be, like, shaggy farm music. But no, Sylvan Esso adheres to the increasingly popular Purity Ring/Chvrches beats-plus-vocals formula. And if you judge Sylvan Esso purely as a festival-synthpop act, they’re a great example of a fast-growing genre. Their vocals are clear and bright and crystalline. Their beats are smart and intuitive, toying around with dance-music textures while only rarely going full thump-thump-thump. Their choruses tend to explode in gloriously, the way these choruses should. Meath layers her vocals in interesting ways, turning herself into an Auto-Tuned backing choir or singing her own counter-harmonies (the parts her bandmates would sing when she’s singing in Mountain Man). And as a singer, Meath is rhythmically inclined enough to turn Sanborn’s beats into playgrounds, dancing through them while staying in the pocket, making sure she’s a part of the beat. (The single “Coffee” is about dancing, among other things, and Meath seems to know what she’s singing about.) Don’t be shocked if Sylvan Esso tracks start showing up in car commercials, or if Danny Brown throws a verse onto one of them, or something like that. They’re that sort of group, and they succeed absolutely based on the sort of criteria you use to judge that sort of group.

But no matter how much twinklethump we might hear in these songs, Meath remains, unmistakably, a folk singer, and you get the idea that these songs would work as folk songs. The project started when Meath asked Sanborn to remix “Play It Right,” a Mountain Man song that Meath had written. It’s very much a Sylvan Esso song now, and its blips and pings make perfect sense where they are. But you can still hear the skeleton of the Mountain Man song underneath, and it would still sound pretty great if it was nothing but voices intertwining. Album closer “Come Down” essentially is nothing but voices intertwining. It starts out with Meath singing entirely a cappella, and even after her doubled-up voices and an electronic hum come in, the song has no drums and no central pulse. Instead, it’s a soft and pretty coffeehouse sigh of a song, with Sanborn’s electronics adding subtle but crucial shadings. “HSKT” is a straight-up house track, and it’s the most rhythmically lockstep track on the album, but its electronic percussion mirrors the sound of stomps and claps. The title’s initials stand for “head shoulders knees toes,” and it’s practically a square-dance song, the sort of thing you would’ve once learned at summer camp, but somehow yanked into the present and charged with a kinetic sort of vitality. On paper, none of this looks like it should work. But all of it does.

Meath and Sanborn recorded Sylvan Esso together in Sanborn’s Durham bedroom, and there’s an appealingly casual air to it, like these two are just trying out some ideas that didn’t fit into their main projects, during the rare moments when their main projects weren’t keeping them busy. (Mountain Man haven’t put out much music lately, but they were Feist’s backing singers throughout her entire Metals tour, which kept them on the road for about two years.) At the same time, we get to hear two people pushing each other out of their respective comfort zones, carving out space in genres of music that might not come naturally to them. And there’s a real artistic chemistry at work; all the pieces just sound right together. Most of the albums that I’ve loved this spring have been dark, overwhelming, monolithic affairs (including Swans’ To Be Kind, which would’ve been Album Of The Week if I hadn’t already written the Premature Evaluation, and which might well be the best album anyone releases this year). But it’s a pleasure and a relief to hear an album like this — a breezy, joyous piece of work, an album that sounds like spring.